This invention involves a device suitable for angioplasty that allows its use as a single operator exchange catheter (rapid exchange) and optionally also allows the continued flow of blood distal to the catheter throughout the balloon inflation period of the procedure.
The objective of the first angioplasty procedure described by Grundzig in 1977 was to be able to relieve the blockages that can occur within coronary arteries blood vessels that feed the heart muscle). These blockages (or stenoses) occur most commonly from atherosclerotic disease causing a lipid laden plaque to develop on the inner surface of a blood vessel wall. Stenoses may also arise from other processes such as radiation injury or diseases such as fibromuscular dysplasia. The procedure was designed to relieve these obstructions and restore blood flow by the use of a distensible balloon on the distal end of a catheter shaft. Once placed across an obstruction within the vascular lumen, inflation of the balloon causes distention of the inner lumen of the blood vessel and a decrease in the blockage such that when the balloon is deflated the result is a larger lumen with a smaller stenosis. The angioplasty procedure has become commonly used in medical practice. It is performed via a percutaneous approach and therefore avoids the need for surgery. Percutaneous angioplasty is most frequently used in the arteries of the coronary, renal, and the peripheral circulations of the human body; however, its use in the cerebral and other vascular beds is also possible.
The standard angioplasty procedure begins with access to the cardiovascular space under local anesthetic and placement of a guiding catheter to the ostium of a coronary artery. The guiding catheter allows the introduction of a radio-opaque dye into the site for visualization of any stenoses. This visualization permits appropriate sizing of a balloon dilatation catheter. Subsequent to this, a guidewire is placed through the guiding catheter up to and across the vascular stenosis. An angioplasty catheter is then advanced over the guidewire, but still within the guiding catheter, until the balloon on the distal tip of the catheter is across the area of stenosis. Inflation of the balloon, also with radio-opaque contrast, causes distention of the vascular lumen and stenosis, and then deflation leaves a larger lumen with compressed plaque, thrombus, fibrous and/or other tissue. The net result is to increase the cross sectional area or lumen of the blood vessel and ultimately to improve the amount of blood flow present at the termination of the procedure.
The angioplasty procedure as currently practiced often requires the use of more than one catheter. The placement of a standard angioplasty catheter over a guidewire requires that a length of wire protrude outside the patient that is longer than the catheter itself. This allows the operator to always be able to maintain contact with the external guidewire while advancing the balloon into the patient, to be able to maintain the distal guidewire across the lesion of interest and to maintain a grip on the guidewire during catheter removal. Having to reinsert a guidewire takes extra time and increases the risk of the procedure. The length of wire required to perform this procedure can include as much as 150 to 200 cm protruding from a patient. This length must be kept sterile throughout the procedure and usually requires a second person in sterile scrub to hold it and maintain it within the sterile field.
Catheter systems have been designed that allow the advancement or removal of an angioplasty catheter over a guidewire by a single operator while not losing the ability to hold the guidewire, i.e., so called rapid exchange catheters. The use of a rapid exchange system reduces guidewire length, decreases the risk of a break in sterility and obviates the need for an assistant during the procedure. Additionally, having to advance a conventional catheter along the entire length of a guidewire imposes significant friction, taxing the operator's ability to push the catheter. This friction also detracts from the physician's sense of tactile response which is important to the success of the procedure.
Current rapid exchange catheters have set distances from the distal tip of the shaft where the guidewire exits the shaft through the proximal exit site. These distances are long enough that they can lead to difficulty for the physician in having to transfer his hold on the guidewire to the angioplasty catheter, risking movement of the guidewire. Other prior art systems place the port for the guidewire on the exterior surface of the balloon such that, in its inflated state, the profile of the balloon-guidewire combination would not allow symmetric deployment of an intracoronary stent. The importance of adequate apposition of stent struts to the vessel wall at deployment is now known to be of great importance in reducing the rates of acute vessel closure and follow-up restenosis. For rapid exchange catheters see U.S. Pat. No. 4,762,129, and U.S. Pat. No. 5,061,273.
All of these catheters have undesirable characteristics of one sort or another. There remains a need for an improved rapid exchange catheter, e.g., having as low a profile as possible, requiring as short a length of guidewire outside the patient as possible and permitting symmetrical deployment of stents when needed.
Another problem associated with the use of standard angioplasty balloons is their inability to permit the distal perfusion of the blood vessel when the balloon is inflated. Thus, there exist potential complications from the resulting cessation of blood flow within the vascular space. These complications are the direct result of balloon inflation and increase as the time without blood flow lengthens. The result can be myocardial ischemia (inadequate blood flow to the heart muscle) manifested by the patient having chest pain, arrhythmias, myocardial infarction or even death. In addition, the use of standard angioplasty balloons is associated with arterial injury. The denuding of the vascular endothelium allows the release of mediators of the inflammatory response which causes platelet activation leading to thrombus formation. This is associated with a 2-5% incidence of abrupt closure of the vessel which can also lead to myocardial infarction, the need for emergency bypass surgery or death.
Perfusion angioplasty dilatation catheters are designed to permit blood flow distal to the inflated balloon for the purpose of limiting these potential complications. In a randomized trial of a perfusion balloon compared with a non-perfusion balloon in the treatment of patients undergoing elective angioplasty, patients treated with prolonged inflations using the perfusion balloon had a higher procedural success rate and a lower rate of arterial injury than those treated with standard balloons and shorter inflation times.
Another long term issue that plagues the angioplasty procedure is the problem of restenosis at the site of balloon dilatation that occurs within six months in 30 to 50% of patients. While the use of a perfusion angioplasty catheter has not been shown to reduce the rate of restenosis at six months of follow-up, recent experiments with the use of intracoronary irradiation show considerable promise in reducing restenosis rates. In both experimental animals and humans, intracoronary irradiation has decreased the follow-up restenosis rate. The delivery of radioactive seeds on the end of a guidewire appears to require the use of a balloon angioplasty catheter for the purpose of centering the seeds within the vascular space for symmetric radiation delivery. A perfusion catheter is also required to provide distal perfusion while allowing the seeds to remain in place for 20 to 30 minutes, the estimated time required to deliver the appropriate radioactive dose in situ.
Many non-perfusion angioplasty catheters have been disclosed with their respective methods of construction, preparation and usage. See, e.g., the disclosures of U.S. Pat. No. Reissue 33,166 and U.S. Pat. Nos. 4,169,263, 4,323,071, 4,411,055, 4,571,240, 4,573,470, 4,582,181, 4,597,755, 4,616,653, 4,619,263, 4,638,805, 4,641,654, 4,664,113, 4,692,200, 4,748,982, 4,771,776, 4,771,778, 4,775,371, 4,782,834, 4,790,315 and 4,793,350.
There are also several known perfusion angioplasty catheters. U.S. Pat. No. 4,581,017 represents the only commercially marketed perfusion catheter presently available in the United States. It provides distal coronary perfusion through the central catheter shaft via serial ports just proximal and also distal to the balloon. Blood flow travels through the center of the balloon. The drawbacks of this technology include the need to retract the guidewire for perfusion to occur, as well as the relatively high profile of the device limiting its use in smaller vessels. In addition, blood flow distal to the catheter is limited by the inner diameter of the central shaft and is usually considerably less than normal (e.g., .ltoreq.40 ml/min, where normal=80-100 ml/min) in the case of coronary blood flow.
Other perfusion catheters also have been disclosed. See, e.g., U.S. Pat. Nos. 5,078,685, 4,909,252, 5,108,370, 5,470,314, 5,433,706, 5,472,425, 5,295,959, 5,370,617, 4,944,745, 5,425,709, 4,790,315, 5,308,356, 5,383,890, 5,395,333, 5,395,353, 5,284,473, 5,484,412, 4,850,969, 5,378,237, 5,425,714, 5,403,274, 5,158,540, 5,318,535, 4,771,777, 5,046,503, 5,484,411, 5,295,995 and 5,383,856. However, all of these are unsatisfactory in one aspect or another, e.g., manufacturing issues or potential application limitations due to size or other design features.
Therefore, the availability of a perfusion angioplasty catheter that is easy to manufacture, does not require use of a central lumen of the shaft for blood flow and does not increase catheter profile would be advantageous to the interventional cardiology profession.